This invention relates to a metalworking fluid that has lubricating and extreme pressure/anti-wear properties and is environmentally safe, biodegradable, and non-hazardous, comprising a vegetable oil such as soybean oil combined with a polar phosphorous-based extreme pressure additive.
Soybean oil and other vegetable oil triglycerides are known lubricants, but present problems as metalworking fluids, including gumming and residue formation. Lightcap, U.S. Pat. No. 6,204,225. Modified oils can impart improved properties but can complicate processing and add expense. Biodegradable triglyceride-based lubricants are described in e.g. Stewart et al., U.S. Pat. No. 4,948,521 and Naegely, U.S. Pat. No. 5,641,734. Oil lubricating additives are also known, e.g. O'Brien, J. A., Lubricating Oil Additives, Handbook of Lubrication, p. 301-315, Vol. II, Edited by E. Richard Booser, CRC Press, Inc., 1984; Gergel, W. C., Lubricant Additive Chemistry, The International Symposium Technical Organic Additives—and Environment, Interlaken, Switzerland, May 24-25, 1984, The Lubrizol Corporation. Conventional mineral oil based fluids with chlorine-free sulfur-based extreme pressure agents are described in U.S. Pat. No. 5,908,816.
Most traditional metalworking fluids are based on mineral oils that present potential environmental hazards. These formulations have been widely used for about thirty years. The most difficult metalworking applications (such as fine-blanking heavy gauge carbon steels, broaching, and drawing of stainless steel tubes and wires) require high performance metalworking fluids containing chlorinated paraffins. Recently however, the use of chlorinated paraffins has been questioned due to hazards to workers and the environment. The corrosiveness of chlorinated paraffins' decomposition products, primarily hydrogen chloride, is a concern. A more serious problem is presented at incineration facilities where incineration temperatures are not high enough, producing highly toxic and cancer-causing waste products. Previous attempts to use non-chlorinated replacements have failed in metalworking requiring high performance lubricating and extreme pressure/anti-wear properties.
There is a need for a high performance, economical, environmentally safe metalworking fluid. There is a growing need for effective, biodegradable soy-based straight oil and soluble oil metalworking fluids. For example, Section 9002 of the 2002 Farm Bill mandates federal procurement of biobased products. However, no existing preparations have been able to effectively replace chlorine-containing mineral oil-based metalworking fluids. There is no known metalworking fluid based on a vegetable oil with a phosphorous-based extreme-pressure additive.